Previously, if a version conflict occurred and a previous primary
response was present, the original primary response would be used both
for sending to replica and back to client. This was made in the past as an
attempt to fix issues with conflicts after relocations where a bulk request
would experience a closed shard half way through and thus have to retry
on the new primary. It could then fail on its own update.

With sequence numbers, this leads to an issue, since if a primary is
demoted (network partitions), it will send along the original response
in the request. In case of a conflict on the new primary, the old
response is sent to the replica. That data could be stale, leading to
inconsistency between primary and replica.

Relocations now do an explicit hand-off from old to new primary and
ensures that no operations are active while doing this. Above is thus no
longer necessary. This change removes the special handling of conflicts
and ignores primary responses when executing shard bulk requests on the
primary.

Previously, if a version conflict occurred and a previous primary
response was present, the original primary response would be used both
for sending to replica and back to client. This was made in the past as an
attempt to fix issues with conflicts after relocations where a bulk request
would experience a closed shard half way through and thus have to retry
on the new primary. It could then fail on its own update.

With sequence numbers, this leads to an issue, since if a primary is
demoted (network partitions), it will send along the original response
in the request. In case of a conflict on the new primary, the old
response is sent to the replica. That data could be stale, leading to
inconsistency between primary and replica.

Relocations now do an explicit hand-off from old to new primary and
ensures that no operations are active while doing this. Above is thus no
longer necessary. This change removes the special handling of conflicts
and ignores primary responses when executing shard bulk requests on the
primary.

Previously, if a version conflict occurred and a previous primary
response was present, the original primary response would be used both
for sending to replica and back to client. This was made in the past as an
attempt to fix issues with conflicts after relocations where a bulk request
would experience a closed shard half way through and thus have to retry
on the new primary. It could then fail on its own update.

With sequence numbers, this leads to an issue, since if a primary is
demoted (network partitions), it will send along the original response
in the request. In case of a conflict on the new primary, the old
response is sent to the replica. That data could be stale, leading to
inconsistency between primary and replica.

Relocations now do an explicit hand-off from old to new primary and
ensures that no operations are active while doing this. Above is thus no
longer necessary. This change removes the special handling of conflicts
and ignores primary responses when executing shard bulk requests on the
primary.

* elastic/master:
  Avoid double term construction in DfsPhase (elastic#38716)
  Fix typo in DateRange docs (yyy → yyyy) (elastic#38883)
  Introduced class reuses follow parameter code between ShardFollowTasks (elastic#38910)
  Ensure random timestamps are within search boundary (elastic#38753)
  [CI] Muting  method testFollowIndex in IndexFollowingIT
  Update Lucene snapshot repo for 7.0.0-beta1 (elastic#38946)
  SQL: Doc on syntax (identifiers in particular) (elastic#38662)
  Upgrade to Gradle 5.2.1 (elastic#38880)
  Tie break search shard iterator comparisons on cluster alias (elastic#38853)
  Also mmap cfs files for hybridfs (elastic#38940)
  Build: Fix issue with test status logging (elastic#38799)
  Adapt FullClusterRestartIT on master (elastic#38856)
  Fix testAutoFollowing test to use createLeaderIndex() helper method.
  Migrate muted auto follow rolling upgrade test and unmute this test (elastic#38900)
  ShardBulkAction ignore primary response on primary (elastic#38901)
  Recover peers from translog, ignoring soft deletes (elastic#38904)
  Fix NPE on Stale Index in IndicesService (elastic#38891)
  Smarter CCR concurrent file chunk fetching (elastic#38841)
  Fix intermittent failure in ApiKeyIntegTests (elastic#38627)
  re-enable SmokeTestWatcherWithSecurityIT (elastic#38814)